1. Field of the Invention
Method for continuous measuring of dynamic fluid consumption, particularly gaseous or liquid motor fuel, by means of a continuous operating flow sensor with variable decrease in pressure, preferably a mass flow sensor, as well as a device to carry out the method comprising a preferably controllable pump, possibly a conditioning device and a fuel tank, and a continuously operating flow sensor for the fluid, preferably a Coriolis sensor.
2. The Prior Art
Intermittently-working systems based on weighing devices are known in the art in measuring consumption of fluids, especially in the use of measuring the liquid fuel consumption of engines on test benches. These devices have the advantage of being open systems, namely they have the characteristic feature that the fuel can be supplied to a user by the measuring system or can occasionally be returned into the system in limited amounts. The supplied and the returned quantity of fuel are recorded by the measuring method and are considered in the reading of total consumption. Open systems are especially advantageous in modern fuel injection system since the latter push back fuel, within limits, into the fuel supply system—particularly the tank in motor vehicles—at the start of the engine and during the pressure buildup in the fuel injection system. However, such weighing devices are of disadvantage in that they have to be filled up repeatedly and continuous measuring is not possible thereby.
Measuring devices are often used for continuous measuring of fuel consumption by performing volumetric measurements of the flow. The used fuel mass as the actual required measurement value is determined by means of an additional density measurement. Direct measurement of mass consumption, which avoids the disadvantage of additional density measuring, can be realized at the present only intermittently with the weighing method for liquid fuels and continuously only with Coriolis sensors for gaseous fuels.
Modern internal combustion engines require mostly defined pressure conditions within the fuel supply line as well as in the possibly existing fuel return line for proper operation, said pressure conditions independent from the fuel flow.
In the Austrian utility model No. 3.350 there is provided a pressure stabilization device, for example, to stabilize the input pressure of the mass flow sensor and to be able to create the required low and constant output pressure (generally of a few millibar) at the connection point to the user. The flow-dependent pressure drop (up to sometimes 2 bar) must therefore be variably compensated at the mass flow sensor. In particular, high frequency, erratic or pulsating-type drawing of fuel from the system must be rapidly taken into consideration.
A pressure regulator is attached upstream from the actual flow sensor for pressure stabilization in the above-mentioned continuous method for fuel measurement. Said pressure regulator adjusts the flow-dependent pressure to a constant outgoing pressure at the discharge point of the measuring system. It is of disadvantage in the arrangement of this type that conventional mechanical pressure regulators act like a “hydraulic diode”, which means that the flowing medium can flow through the regulator only in one direction, namely downstream. A measuring system having such a pressure regulator is not an open system. Should fuel have to be returned from the injection system back into the measuring system or should there occur thermal expansion of the fuel caused by a temperature increase in the fuel circuit when the user has stopped operation, then there is created a mostly inadmissibly high pressure increase in the fuel system—depending on the elasticity of the tubing—and it places stress on the lines and components which must be relieved possibly by costly pressure compensation devices.
The object of the present invention is to provide a method and a device which make possible accurate and rapid consumption measurements with controlled outgoing pressure for the liquid or gaseous fluid by means of an open system and which also allows a short time return flow during simultaneous measuring of the flow.